JPS634247A - Negatively electrifiable developing agent - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a developer for developing latent images in electrophotography, electrostatic recording, electrostatic printing, and the like. More specifically, in the direct or indirect electrophotographic development method, the electrostatic charge image is uniformly and strongly negatively charged, a positive electrostatic charge image is visualized (in the case of reversal development, a negative electrostatic charge image is visualized), and a highly This invention relates to an electrophotographic developer that provides high-quality images.

[Conventional technology]

Conventionally, regarding electrophotography, U.S. Patent No. 2.297,
No. 691, Japanese Patent Publication No. 42-23910 (US Patent No. 3.666).

As described in Japanese Patent Publication No. 43-24748 (U.S. Pat. No. 4,071,361), the photoconductive layer is uniformly charged and light is emitted according to the original. A latent image is formed by extinguishing the charge in the exposed area by imagewise exposure, and development is carried out by attaching a fine powder electrostatic substance, so-called toner, to the obtained electrostatic latent image.
The toner is attracted to the electrostatic latent image depending on the amount of charge on the photoconductive layer, forming a toner image with shading. This toner image is transferred to a support surface such as paper or cloth as necessary, and permanently fixed on the support surface by heating, pressure, a heated pressure roller, or the like. Alternatively, if it is desired to omit the toner image transfer step, the toner image can be fixed to the photoconductor layer. In addition to the fixing method described above, it is also possible to use other means such as solvent treatment and overcoating treatment.

There are many known development methods for this electrophotography.
Until now, the cascade development method described in U.S. Patent No. 2,618.552, which is a development method used as a secondary toner by mixing with carrier particles, and U.S. Patent No. 2,874,
The magnetic brush method described in No. 063 has been widely used.

All of these methods are excellent methods in which good images can be obtained relatively stably, but on the other hand, they have common problems related to the secondary developer, such as deterioration of the carrier and fluctuations in the mixing ratio of toner and carrier.

In order to avoid such problems, various development methods using a one-component developer made only of toner have been proposed, among which many are superior to methods using a developer made of magnetic toner particles.

US Pat. No. 3,909,258 proposes a developing method using an electrically conductive magnetic toner. This supports a conductive magnetic developer on a cylindrical conductive toner carrier (sleeve) that has magnetism inside.
This is brought into contact with an electrostatic image and developed.

At this time, a conductive path is formed by the toner particles in the developing device between the surface of the recording medium and the sleeve surface, and through this conductive path, an electric charge is guided from the sleeve to the toner particles, and a Coulomb force is generated between the electrostatic image and the image area. The toner particles adhere to the image area and are developed.

This developing method using conductive magnetic toner is an excellent method that avoids the problems associated with conventional two-component developing methods, but on the other hand, because the toner is conductive, the developed image can be transferred from the recording medium to the final product such as plain paper. The problem is that it is difficult to electrostatically transfer the image onto a support member.

There is a developing method using dielectric polarization of toner particles as a developing method using a high-resistance magnetic toner that can be electrostatically transferred. but.

Such a method inherently has a slow development speed; i! i
This method has problems such as insufficient i-image density and is difficult in practice.

Other developing methods using high-resistance magnetic toner include
A known method is to triboelectrically charge toner particles by friction between toner particles or friction between toner particles and a sleeve or the like, and then develop the toner particles by bringing them into contact with an electrostatic image holding member. but,
The first problem with these methods is that the number of times of contact between the toner particles and the friction member is small, which tends to result in insufficient triboelectric charging, and the charged toner particles tend to aggregate on the sleeve due to the strong Coulomb force between them. This was difficult in practice.

The applicant has previously proposed a new developing method that solves the above-mentioned problems in Japanese Patent Laid-Open No. 55-42141. This is a method in which an extremely thin layer of insulating magnetic toner is applied onto a sleeve, which is then triboelectrically charged.Then, it is placed very close to the electrostatic image under the action of a magnetic field, and developed by causing the toner to fly. It is.

According to this method, the degree of contact between the sleeve and the toner is increased by applying an extremely thin layer of magnetic toner onto the sleeve, and sufficient frictional electrification is made possible, and the toner is supported by magnetic force.

In addition, by moving the magnet and toner relatively, the toner particles are disaggregated and sufficiently rubbed against the sleeve, and the toner is supported by magnetic force, and the toner is opposed to the electrostatic image without coming into contact with it. Excellent images can be obtained by developing the image using a dry process to prevent blurring.

However, even in this method, the amount of tripo charge that the toner particles coated on the sleeve have is significantly smaller than the amount of tripo charge that the toner particles have in normal secondary development.

If magnetic toner with only a weak charge is used in this way, the image will have low density, scattering, smearing, etc.
Image unevenness occurred, and the image quality was insufficient.

In particular, the initial image density is low, and usually several hundred copies are required to stabilize it to a good high degree of stability, and this instability in start-up is one of the major problems in one-component system development.

In order to solve this rising instability, it is possible to improve the tripostatic charge amount of the toner, and the means to do so are as follows:
It is known to add silicic acid fine powder to a developer having negative chargeability.

In this case, since the silicic acid (silicon oxide) vIL particles themselves have negatively charged properties, they can serve as an adjuvant for good retention of negative charges in negatively charged toners. However, r
Since the toner has a negative charge and the silicic acid fine particles also have the same negative charge, electrostatic repulsion works and it is difficult to properly apply the silicon oxide fine particles to the toner. During the phase, there was a tendency for low image density and a noticeable drop in image density, followed by a noticeable rise phenomenon.

[Problem that the invention seeks to solve]

An object of the present invention is to provide a developer having stable and uniform negative chargeability. Still another object is to provide a developer which has high image density from the beginning without any drop in image density.

Still another object is to provide a developer that does not cause rise in image density and provides high image density from the beginning.

Still another object is to provide a developer with excellent storage stability that maintains its initial characteristics even during long-term storage.

Still other purposes are high temperature, low temperature, and high humidity.

It is an object of the present invention to provide a negatively charged developer that is not easily affected by environmental changes such as low humidity.

[Means and actions for solving the problem] The characteristics are that the developer is a negatively charged developer, and a negatively charged toner is: Electrolytic hydrophobized silicic acid fine powder; exhibits lower frictional charging properties than the toner, and has a particle size larger than the silicic acid fine powder and smaller than the toner, and has a volume average particle size of 1.0 to 4.0 gm. The loss on heating up to 100°C is 0.5% by weight or less, and the B
A negatively charged developer comprising at least a microdisperser having an ET specific surface area of 15 m 2 /g or less.

In other words, the present inventors found that negatively charged hydrophobized silicic acid fine powder exhibits charge controllability when contained in a developer, but this alone is not sufficient to provide sufficient negative charge controllability or to prevent long-term storage. It was difficult to maintain initial characteristics and withstand environmental changes. On the other hand, the inventors of the present invention have found through studies that the above characteristics can be improved by mixing a third fine powder (hereinafter referred to as a microdisperser).

In the present invention, the microdisperser, which is a component of the developer, has a volume average particle diameter of 1.0 to 4.0 μm (preferably 1.5 μm) as measured using an L-zone counter.
~3.5pm), and the specific surface area by BET method is 15
m2/g or less, and the temperature is 20℃ and the relative humidity is 90℃.
% or more, the weight loss on heating up to 100°C is 0.5 wt% or less, which is smaller than the volume average particle size of the toner and larger than the particle size of the hydrophobized silicon oxide fine particles. Furthermore, a material having lower frictional charging properties than toner is used.

The volume average particle diameter measurement in the present invention was carried out using an Elzone counter using a 24-m orifice. The L-Zone counter is similar in principle to the Coulter counter, but by having a large number of divided channels and using a small diameter orifice, it is possible to
Fine particle size distribution in the range of ALm can be measured more accurately. In addition, the measurement of the specific surface area by the BET method in the present invention is carried out using an automatic specific surface area measurement device. Nitrogen gas (N2) is adsorbed onto a powder sample, and the ratio is determined from the changed gas amount and sample weight. This is to find the surface area.

In the present invention, the loss on heating up to 100''0 is measured by leaving the particles in a desiccator (temperature 20°C, relative humidity 90% or higher) conditioned with a saturated ammonium chloride solution for 72 hours, and then discarding approximately 50 mg of the particles. It is possible to take a sample and measure it using, for example, DTA-TG (manufactured by Rigaku Denki, differential thermometer) without using a carrier gas.

The microdisperser used in the present invention has a volume average particle size of 1 to 4 μm as described above. When a microdisperser with a volume average particle size of 1 gm or less is used, the aggregation of the microdisperser As a result, the behavior as free particles decreases, and as a result, the stirring ability decreases. In addition, when a microdisperser with a volume average particle size of 4 gm or more is used, the particle size of the hydrophobized silicon oxide fine particles becomes large, so that the ability to dissociate aggregates of the silica fine particles and the stirring ability are reduced. Therefore, the ability to suppress a decrease in initial image density and falling and rising phenomena is reduced. Similarly, in the case of a microdisperser having a heating loss value and a BET specific surface area outside the range specified in the present invention, the fluidity and moisture resistance of the microdisperser itself are poor, and the ability to roughly loosen and separate silica aggregates is poor. As a result, the effectiveness of the microdisperser intended by the present invention deteriorates. By adding a specific microdisperser to a mixture of negatively charged toner and hydrophobized silicon oxide particles, the hydrophobized silicon oxide fine particles exhibit strong negative chargeability, and In addition to its role as a fluidizing agent, it also satisfactorily serves its role as a charge imparting agent. This shows that when hydrophobic silicon oxide fine particles are added to a developer, the difference is greater than that of a developer without the addition of hydrophobic silicon oxide fine particles.

There is even an analogy since the concentration increases markedly.

In addition, even in the early stages of development, the hydrophobized silicon oxide fine particles and the toner are sufficiently stirred, and the hydrophobized silicon oxide fine particles are well dispersed between the toner particles, allowing charge to be transferred to the toner. Enough is done. This achieves an improvement in the initial concentration and suppression of fall and rise. When observed under a microscope, many aggregated toner lumps and aggregates of silicon oxide fine particles can be seen in the developer that does not contain a microdisperser, but such aggregates are not observed in the developer that contains a microdisperser. From the fact that there is no or very little amount of silicon oxide powder, and that the latter shows extremely good fluidity between the two, it can be understood that the microdisperser has aS that can disperse silicon oxide fine powder well into the toner. I can do it. In fact, observation of the toner surface with and without a microdisperser shows that the amount and adhesion state of silicon oxide particles adhering to the toner are significantly different in the developer with a microdisperser. is observed to be extremely finely dispersed and evenly adhered to the toner surface, whereas in the developer that does not contain a microdisperser, silicon oxide fine particles are unevenly distributed on a part of the toner surface in a form close to agglomerates. It is known that In addition, in developers containing microdispersers, microdispersers with silicon oxide fine particles attached around them can be seen, so microdispersers are used to loosen and disperse agglomerates of such silicon oxide fine particles. It is also assumed that the silicon oxide particles act as a carrier for the silicon oxide particles and play a role in supplying the silicon oxide particles to the toner. Therefore, in the relationship between negatively charged toner and negatively charged silicon oxide fine particles, the microdisperser acts particularly on the negatively charged silicon oxide fine particles to break up their agglomeration and quickly oxidize the negatively charged toner. It is thought that it supplies silicon fine particles. The reason why the microdisperser acts selectively on silicon oxide fine particles over toner is probably because the silicon oxide fine particles have a potentially higher negative charge ability than the toner, and at the same time, the silicon oxide fine particles It is assumed that this is because the diameter is closer to that of the microdisperser than that of the toner, and the triboelectric charging property of the microdisperser is lower than that of the toner. Therefore, it is preferable that the triboelectricity of the microdisperser is low, and this is determined by the amount of triboelectric charge Q (JLc
/g), IQ+≦3 (pc/g) is preferred.

For example, when left unused for a long period of time, negatively charged toner and negatively charged silicon oxide fine particles tend to separate or aggregate, resulting in deterioration of properties. The fine particles must be stirred and mixed, and if they have already been left in the developing device, they must wait until they are gradually recovered by a stirring device or the like within the developing device.

On the other hand, in the present invention, in the case of a developer containing a specific microdisperser, silicon oxide fine particles are quickly supplied into the negatively charged toner by the action of such a stirring device and the microdisperser, so that there is almost no deterioration. This is consistent with the fact that the phenomenon is not observed.

Metal oxides are preferred as microdispersers.
For example, CeO2, Cu2O.

There are particles whose main components are Ta205, Sro, La2O3, etc. Among these commercially available metal oxides,
Those applicable to the physical properties of the present invention are used. In particular, when the microdisperser is cerium oxide particles, Miracle T (manufactured by Mitsui Kinzoku Kogyo ■) is a specific cerium oxide particle that meets the physical properties of the present invention.
Commercial products such as ROX M-1 (manufactured by Mitsui Kinzoku Kogyo Co., Ltd.) and ROX M-3 (manufactured by Tohoku Kinzoku Kagaku ■) can be mentioned.

The commercially available cerium oxide particles contain little or no mixing of ultrafine silica and silicate sol, which are usually added during production as an abrasive for optical glass, and the firing temperature is also lower than that for ordinary abrasives. It is manufactured by pulverizing and classifying after firing to remove coarse particles, and is preferably used in the present invention.

These microdispersers are used in an amount of 0.01-10 parts by weight per 100 parts by weight of toner.

Preferably, 0.1 to 5 parts by weight are mixed.

If the amount of microdisperser is less than this, the effect of the present invention will be weakened, and if it is more than this, it will have an adverse effect on toner charging control, and there will be a strong tendency for density reduction, density fluctuation, etc. to occur.

In the present invention, the negatively charged silicon S fine powder, which is one of the constituent components of the developer, has a charge amount of -20hC/
g or more is preferable. Especially 230 to -300 ru c
/g, and preferably has a larger value than a toner to which the fine silicic acid powder and microdisperser are not added.

In the measurement of the amount of charge (frictional tripo value) in the present invention, the test substance is mixed with an iron powder carrier having a particle size of 200/300 mesh.

In the case of hydrophobic silica, the ratio of test substance to carrier is 2:1.
00 If the test substance is a microdisperser or toner, mix at a ratio of 10:90. The mixture is 0.5-1
．． Weigh 5g accurately and place it on a metal 400 mesh screen connected to an electrometer as shown in Figure 1.
It is suctioned with a pressure of 25 cmH2O, and the amount of charge per unit mold 2 is determined from the separated and suctioned test substance and its amount of charge.

The particle size of the silicic acid fine powder of the present invention is 3 gm or less, particularly 0.0 gm or less.
The amount is preferably about 1 to 1 uL, and can be calculated by randomly selecting 20 or more particles from a transmission electron microscope photograph and measuring their diameters.

As the silicic acid fine powder used in the present invention, silicic acid fine powder produced by a dry method or a wet method can be used.

The dry method mentioned here is a method for producing fine silica powder produced by the above-mentioned phase oxidation of a silicon halide compound.

Commercially available fine silica powder produced by vapor phase oxidation of a silicon halogen compound used in the present invention includes, for example, those commercially available under the following trade names.

AERO3IL 130 (Japan Aerosil Co., Ltd.) 200 oxs.

T600 0X80 0X170 0K84 Ca-0-SiL M-5 (CABOT
Co., Ltd.) MS-7S-5 H-5 Wacker HDK N 20
V 1 5 (WACKER-CHEMI
E 0M88) N20ED-CFine
5ilica (Dow Corning Co., Ltd.) Franso 1 (Fransi 1 Co., Ltd.) On the other hand, various conventionally known methods can be applied to the method of producing the silicic acid fine powder used in the present invention by a wet method.

The silicic acid fine powder mentioned here is anhydrous silicon dioxide (
Silica) is a typical example, and other silicates such as aluminum silicate, sodium silicate, potassium silicate, magnesium silicate, and zinc silicate can be used.

Further, the silicic acid fine powder used in the present invention is further hydrophobized using a conventionally known hydrophobizing agent.

A known method is used for this purpose, and it is applied by chemically treating the silicic acid fine powder with an organosilicon compound that reacts with or physically adsorbs on the silicic acid fine powder. Examples of such organosilicon compounds are hexamethyldisilazane, trimethylsilane.

trimethylglorsilane, trimethylethoxysilane,
Dimethyldichlorosilane, methyltrichlorosilane, allyldimethylchlorosilane, allyl phenyldichlorosilane, benzyldimethylchlorosilane, bromomethyldimethylchlorosilane, α-chloroethyltrichlorosilane, β-chloroethyltrichlorosilane, chloromethyldimethylchlorosilane Silane, triorganosilylmercaptan, trimethylsilylmercaptan, triorganosilylacrylate, vinyldimethylacetoxysilane, dimethylethoxysilane, dimethyldimethoxysilane, diphenyljethoxysilane, hexamethyldisiloxane, 1.3-divinyltetramethyldisiloxane, 1. 3
-diphenyltetramethyldisiloxane, and dimethylpolysiloxane which has 2 to 12 siloxane units per molecule and each unit located at the end contains a hydroxyl group bonded to one St. These may be used alone or in a mixture of two or more.

These hydrophobized silicon oxide fine particles (@aqueous silica) are commercially available, such as R972 manufactured by Aerosil Co., Ltd.
, R-974゜R-976, RY-130, RY-20
0゜RY-300, R-812, T-34 manufactured by Talco
0, T-500, etc.

These silicon oxide fine powders are used in an amount of 0.01 to 10 parts by weight, preferably 1 to 5 parts by weight, per 100 parts by weight of the toner.

When hydrophobic silica, which is hydrophobically treated silicon oxide fine particles, is hydrophobized so that the degree of hydrophobicity is 40% or more as measured by a methanol titration test, such fine silica powder is treated as such. This is preferable because the amount of triboelectric charge of the developer containing it shows sharper and more uniform negative chargeability.Here, the methanol titration test is used to confirm the degree of hydrophobization of the silica fine powder having a hydrophobized surface. be done. The "methanol titration test" defined in the present invention for evaluating the degree of hydrophobicity of the treated silica fine powder is carried out as follows.

0.2 g of the silica fine powder sample is added to 50 m of water in a 250 mJl Erlenmeyer flask. Methanol is titrated from the burette until all of the silica is wetted. At this time, the solution in the flask is constantly stirred with a magnetic stirrer.

The end point is observed when the entire amount of fine silica powder is suspended in the liquid, and the degree of hydrophobization is expressed as the percentage of methanol in the liquid mixture of methanol and water when the end point is reached.

As the binder resin for the toner used in the present invention, known binder resins can be used, for example.

Polystyrene, poly P-chlorostyrene.

Monopolymers of styrene and its substituted products such as polyvinyltoluene; styrene-p-chlorostyrene copolymer, styrene-propylene copolymer, styrene-vinyltoluene copolymer, styrene-vinylnaphthalene copolymer, styrene-acrylic acid methyl copolymer, styrene-ethyl acrylate copolymer, styrene-butyl acrylate copolymer, styrene-octyl acrylate copolymer, styrene-ethyl methacrylate copolymer.

Styrene-ethyl methacrylate copolymer.

Styrene-butyl methacrylate copolymer, styrene-α
- Methyl chlormethacrylate copolymer, styrene-7crylonitrile copolymer, styrene-vinyl methyl ether copolymer, styrene-vinyl methyl ether copolymer.

Styrene-vinyl methyl ketone copolymer, styrene-butadiene copolymer, styrene-isoprene copolymer, styrene-acrylonitrile-indene copolymer, styrene-maleic m copolymer, styrene-maleic acid half ester copolymer, Styrenic copolymers such as styrene-maleic acid ester copolymers; polymethyl methacrylate, polybutyl methacrylate, polyvinyl chloride, polyvinyl acetate, polyethylene, polypropylene, polyester, polyurethane, epoxy resin, polyvinyl butyral.

Polyamide, polyacrylic acid resin, rosin, modified rosin, terpene resin, phenolic resin, aliphatic or alicyclic hydrocarbon resin, aromatic petroleum resin, chlorinated paraffin,
Paraffin, wax, etc. can be used alone or in combination.

If necessary, add a charge control agent (binder resin 1) to this binder resin.
00 parts by weight, preferably 0.1 to 10 parts by weight),
Colorant (preferably 0.00 parts by weight per 100 parts by weight of binder resin)
1 to 10 parts by weight).

The volume average particle diameter of the toner when it is made into particles containing a lubricant etc. is 3 to 30 pm, particularly preferably 5 to 20 pm.
pm is used.

At this time, as shown in the Examples described later, a negative charge control agent of a metal complex of chromium, zinc, or cobalt is preferable.

It is also a particularly preferred embodiment of the present invention.

Insulating magnetic toner (electrical resistance value IQ - 13Ωcm or more)
When the present invention is applied to, the magnetic substance contained in the toner includes ferromagnetic elements and alloys and compounds containing these, such as iron and cobalt such as magnetite, hematite, and ferrite.

Alloys and compounds of nickel, manganese, and other ferromagnetic alloys can be used as appropriate. The magnetic material also acts as a coloring agent.

Its particle size is 100-800 muL, preferably 3
00 to 500 ml, preferably 30 to 100 parts by weight, more preferably 40 to 90 parts by weight, per 100 parts by weight of the binder resin.

In addition, the present invention will not be hindered in any way even if a charge control agent, a flow modifier, a color agent, a lubricant, and the like are added and contained in the magnetic toner as necessary.

In manufacturing the toner of the present invention, a hot roll, a kneader, etc.
A method of obtaining the product by mechanically crushing and classifying the constituent materials after thoroughly kneading them using a heat kneader such as an extruder.

Alternatively, a method is obtained by dispersing a material such as magnetic powder in a binder resin solution and then spray-drying it, or by polymerizing an emulsified ffi liquid prepared by mixing a specified material with the monomers that should constitute the binder resin. Each method can be applied, such as a polymerization method and a toner production method, in which a toner is obtained by

Furthermore, recently, microencapsulated toner and the like have been proposed for the purpose of separating the functions of the toner, but the present invention can be applied as long as the requirements of the present invention are satisfied.

Furthermore, as a method for adding and incorporating the inorganic fine powder into the toner, a known mixer 1 such as a rotating container type mixer such as a type mixer or a tarpaulin mixer, or a fixed container such as a ribbon type, screw type, rotary blade type, etc. A mold mixer can be used as appropriate.

Further, during mixing, the three substances may be mixed at once, or may be mixed in order taking into consideration the properties of the toner, and it is also possible to add a known fourth substance. Examples include polyethylene fluoride, polyvinylidene fluoride, fatty ugly metal salts, various abrasives, and the like.

An example of the method for measuring the amount of triboelectric charge in the present invention will be described.

FIG. 2 is an explanatory diagram of the frictional charge amount measuring device.

A metal measuring container 2 with a conductive screen 3 of 400 mesh (the size can be changed as appropriate so that magnetic particles do not pass through) on the bottom contains the toner or toner constituent fine particles whose triboelectric charge amount is to be measured, and 200 to 300 mesh of conductive screen 3. A mixture of amorphous iron powder (Japanese Iron Powder EFV200/300. The surface is untreated and, like the toner carrier, has virtually no triboelectrification on its own) with a weight ratio of 1:9 ( Add about 4g of developer and close the metal lid 4.

At this time, the entire weight of the measuring container 2 is weighed as Wl (g).Next, in the suction device 1 (at least the part in contact with the measuring container 2 is an insulator), suction is drawn from the suction lower and the air volume control valve 6 is adjusted. The pressure of the vacuum gauge 5 is set to 70 mmHg. Sufficient suction (for about 1 minute) is performed in the second state to remove the toner or the mixture of toner and silicic acid fine powder. At this time, the potential of the electrometer 9 is assumed to be ■ (volts). Here, 8 is a capacitor whose capacity is C (gF). Also, the weight of the entire measurement container after suction is weighed and is W2 (g). This frictional charge amount T (JLc/g) is calculated as shown in the following formula.

However, the measurement conditions are 23° C. and 50% RH.

Hereinafter, the present invention will be explained in more detail using Examples.

In addition, "1 part" indicates "part by weight."

Example 1 100 parts of 9-styrene-n-butyl methacrylate copolymer (copolymerization weight ratio 7:3; Mw = 200,000), 60 parts of magnetite (volume average particle size 0.5 gm), 4 parts of low molecular weight polyethylene - 2 parts of Cr complex monoazo dye (Bontron S-34) The mixture of the above formulation was melt-kneaded, cooled, and then pulverized.

Classified to obtain a particle size of 5 to 20 m (volume average particle size of 12 cm)
) insulating magnetic toner (electrical resistance value 1015Ω・am)
I got it. 100 parts by weight of the obtained insulating magnetic toner was added with a hydrophobicity of 65. Cerium oxide particles containing 0.4 parts by weight of hydrophobic silica with an average primary particle size of 1007h and 80% by weight of CeO2 component [volume average particle size measured by Elzone Counter (manufactured by Particle Data Inc., USA): 2.74 p,
m, heating loss after moisture absorption to lOOoC 0.14% by weight, automatic specific surface area measuring device 220 using nitrogen gas adsorption method
BET specific surface area is 3.6 m when measured with Type 0 (manufactured by Shimabara Seisakusho)
2/g) and 1 part by weight to prepare a developer.

When this developer was applied to a commercially available plain paper copying machine (NP-400 manufactured by Canon) and an image was obtained by continuously copying 500 sheets, the reflection density of the image was 1 as shown in the graph in the attached drawing.
Sheet 1.43.

20th photo 1.38. 50th photo 1.37. 100
Sheet 1.41. The image density was 1.40 on the 500th copy, and there was no drop in image density during initial copying, and the reflection density was stable throughout, at 1.4, with no fog.

An extremely clear image was obtained. Further, the developer of the present invention can be used at high temperature and high humidity (32.5°C, 90%) and at low temperature and low humidity (15°C).
Even under the environment of C910%), the developing characteristics were as good as those under normal temperature and normal humidity.

The toner has a tribo-tripo value of -13 kC/g.

Hydrophobic silica was -110 gc/g, and cerium oxide was -1 stc/g.

Examples 2-6 Each developer was prepared in the same manner as in Example 1, except that the cerium oxide particles shown in Table 1 below were used. The results of the image forming test conducted in the same manner as in Example 1 are shown in Table 2.

Table 1 Example 7 The same procedure as in Example 1 was carried out except that 0.4 parts by weight of hydrophobic silica having a degree of hydrophobicity of about 50 and an average primary particle of 0.0164 m friction tripo value -t20 pc/g was used. Table 2 shows the results of the 0 image forming test in which the developer was prepared.

Example 8 Styrene-2-ethylhexyl acrylate copolymer (copolymerization weight ratio 6:4; Mw = 250,0
00) A developer was prepared in the same manner as in Example 1, except that 100 parts by weight was used. Table 2 shows the results of the zero image forming test in which the toner had a tribo-tripo value of -12 pc/g.

Example 9 Styrene-n-butyl acrylate as a binder resin
Maleic acid monobutyrate copolymer (copolymerization weight ratio 65
: 30 : 5; Mw=420.000) 100
A developer was prepared in the same manner as in Example 1 except that parts by weight were used. The friction tripod value of the toner is -1
It was 4JLc/g. The results of the image formation test are shown in Table 2.

Example 10 A developer was prepared in the same manner as in Example 1, except that 2 parts by weight of alkyl salicylic acid CO complex was used as a charge control agent. The friction tripod value of the toner is -11 tao c
/g.

The results of the image formation test are shown in Table 2.

Comparative Example 1 100 parts by weight of the magnetic toner prepared in Example 1 without blending cerium oxide particles with a degree of hydrophobicity of about 65. A developer was prepared by mixing 0.4 parts by weight of hydrophobic silica with an average primary particle size of 0.007 m friction tripod value -110 gc/g, and an image forming test was conducted in the same manner as in Example 1. .

As shown in the graph in the attached drawing, the reflection density was 1.
10. 20th sheet 0.88. 50th sheet 0.69.
100th sheet 0.70. The image density was low at 1.18 on the 500th sheet, and a falling phenomenon was observed.

Comparative Example 2 To 100 parts by weight of the magnetic toner prepared in Example 1, 0.4 parts by weight of non-hydrophobicized silica with a degree of hydrophobicity O1 and an average particle size of 0-0164 m and a volume average particle size of 3.2 by Elzone were added.
Cerium oxide containing 63.2% by weight of CeO2 with a heating loss of 2.3% by weight at 100°C after moisture absorption and a specific surface area of 39.0m2/gC (outside the specified range of the present invention) by BET method. A developer was prepared by mixing with 1 part by weight of particles. As is clear from the graph shown in the attached drawings, a remarkable drop phenomenon was observed when the number of copies was 50 to 100.

Comparative example 3 Volume average particle size 1.64 gm by Elzone.

Loss on heating at 100°C after moisture absorption: 1.08 parts by weight (outside the specified range of the present invention), specific surface area by BET method: 8.1 m
Example 1 except that 1 part by weight of cerium oxide particles containing 53 parts by weight of CeO2/g is used.
A developer was prepared in the same manner as above. The test results are shown in Table 2.

Comparative example 4 Volume average particle size 1.47 gm by Elzone.

Loss on heating at 100°C after moisture absorption: 1.50 parts by weight, BET
Specific surface by law @ 18. A developer was obtained in the same manner as in Example 1, except that 1 part by weight of cerium oxide particles containing 80 parts by weight of CeO2 having an Om 2 /g content was used. The test results are shown in Table 2.

Comparative Example 5 Oxidation containing 51.8 parts by weight of CeO2 with a volume average particle size of 4.52 gm by Elzone, loss on heating at 100°C after moisture absorption of 0.14 parts by weight, and a specific surface area of 1.8 m2/g by BET method. A developer was prepared in the same manner as in Example 1 except that 1 part by weight of cerium particles was used. The test results are shown in Table 2.

Comparative example 6 Volume average particle size according to Elzone: 0.91 μm.

Loss on heating at 100°C after moisture absorption: 0.08 part by weight.

Cerium oxide particles 1 containing 72.5 parts by weight of CeO2 with a specific surface area of 9.5 m 2 / g by BET method
A developer was prepared in the same manner as in Example 1 except that parts by weight were used. The test results are shown in Table 2.

Comparative Example 7 A developer was obtained in the same manner as in Example 1, except that 0.4 parts by weight of non-hydrophobicized silica with a degree of hydrophobicity of 0 and an average particle diameter of 0.12 μm was used. The test results are shown in Table 2.

In Examples 2 to 10 of Table 2, there was virtually no initial drop in image density, the reflection density was stable from the beginning to the end, and extremely clear images without fog were obtained, but Comparative Examples 2 to 7 ．．
In this case, the initial fall of the image density is remarkable, and the initial drop in image density is 50
In all cases, the reflection density is approximately 0.3 until the first sheet.
The density was lowered to a greater extent than that, and an image quality with noticeable fog, blur, and inferior resolution was obtained compared to the examples of the present invention.

This reveals that the effect of the developer of the present invention is very significant.

Example 11 5 to 20 parts consisting of 100 parts of polystyrene (manufactured by D-125 Bercules), 50 parts of magnetite (EFT-500, manufactured by Toda Kogyo), and 5 parts of an alkyl salicylic acid Cr complex
Hydrophobic colloidal silica (manufactured by Nippon Aerosil) (length and average diameter 0.26 parts m @ hydration degree 70) was added to 100 parts of toner obtained by a conventional method. 1
part, oxidized steel particles (mainly composed of Cu20, volume average particle size 2.36 gm BET specific surface area 9.2 m 2 /
After mixing and preparing a developer consisting of 3 parts (loss on heating: 0.28 parts by weight), it was applied to a commercially available plain paper copying machine (NP-400 manufactured by Canon) to obtain images, and the reflection density was 1.3 to 1.
Very sharp images with no fog of 1.4 were obtained from the first image. When 200 copies were made after this, good density was obtained as in the -th copy, and no variation in density was observed.

Further, a copy image was obtained again after leaving it for 40 days, and the image density was the same as the initial reflection density of <1.3 to 1.4, and an extremely sharp image without fog was obtained.

In addition, when the toner, negatively charged silicic acid fine powder, and copper oxide particles are measured by the method described above, the tripocharges are -12, respectively.
Values of JLc/g, about -180 gc/g, about -1 Lc/g were obtained.

Example 12 100 parts of polystyrene (manufactured by D-125 Bercules), magnetite (EFT-500゜Toda Kogyo Department) 50
5 to 20 parts, consisting of 5 parts of chromium complex type monoa 7r dye
gm (length average diameter 15.3 parts m) toner obtained by a conventional method, 100 parts of hydrophobic colloidal silica (manufactured by Nippon Aerosil) (hydrophobicity degree 65, length average diameter 0.12 gm)
) 0.5 part, tantalum oxide particles (based on Ta205, volume average particle size 3.12 gm).

BET specific surface area 6.5 m 2 / g, heating loss 0
．． After preparing a developer consisting of 2 parts (35 parts by weight), it was applied to a commercially available plain paper copying machine (NP-400 manufactured by Canon) to obtain an image. Very sharp images were obtained from the first shot. After this, 200 copies were made, and images with good density were obtained, similar to the first copy, and no variation in a degree was observed. Furthermore, 4
After leaving it for 0 days, I got a copy again, but it was the same as the initial one.
An extremely sharp image with a reflection density of 1.3 to 1.4 and no fog was obtained. Incidentally, the tripo of this negatively charged silicic acid fine powder was about -1.20 u, c/g. Furthermore, the tripod of the tantalum oxide particles was lower than that of the toner, at -2 gc/g.

Example 13 5 to 20 gm (length average diameter: 11.5 gm) consisting of 100 parts of styrene-2-ethylhexyl acrylate (manufactured by Sanyo Chemical Co., Ltd.), 50 parts of magnetite (EPT-500, Toda Kogyo Department), and 5 parts of alkyl salicylic acid Zn complex. Hydrophobized colloidal silica (manufactured by Nippon Aerosil) (hydrophobicity degree 70, length average diameter 0
．． 23 gm) 1 part, strontium oxide particles (S ro
Volume average particle size 2.15um, BET
Specific surface area 13.7 m2/g.

After mixing and adjusting a developer consisting of 3 parts (heat loss: 0.25 parts by weight), it was applied to a commercially available plain paper copying machine (NP-150Z manufactured by Canon) to obtain an image, and the reflection density was 1.3~
An extremely sharp image with no fog of 1.4 was obtained from the first image. When 200 copies of this were made, images with good density were obtained, similar to the first copy, and no density fluctuation was observed. Further, a copy image was obtained again after being left for 40 days, and the reflection density was 1.3 to 14, which was the same as the initial image, and an extremely sharp image without fog was obtained. The tripo of strontium oxide particles is lower than that of toner;
+ i p-c / g Example 14 100 parts of styrene-2-ethylhexyl acrylate (manufactured by Sanyo Chemical Co., Ltd.), 50 parts of magnetite (EPT-500, Toda Kogyo Department), Zn complex type monoazo dye 5 consisting of 5 parts
2 parts of hydrophobized colloidal silica (manufactured by Nippon Aerosil) (hydrophobicity degree 75, average length diameter 0.08 gm) per 100 parts of toner of ~20 JLm (length average diameter 11.5 gm) obtained by a conventional method. , lanthanum oxide particles (based on La203, volume average particle diameter 2.72 m2, specific surface a7.2 m27 g, loss on heating 0.32 parts by weight)
An image was obtained by mixing and preparing a developer consisting of four parts and applying it to a commercially available plain paper copying machine (NP-400 manufactured by Canon).

Very sharp images with no fog and a reflection density of 1.3 to 1.4 were obtained from the first sheet. When 200 copies of this were made, images with good density were obtained, similar to the first copy, and no density fluctuation was observed. Furthermore, after leaving it for 40 days, I obtained a copy again, but the reflection density was 13, as it was at the beginning.
An extremely sharp image with no fog was obtained with an image density of ~1.4. Incidentally, the tripo of the lanthanum oxide particles was lower than that of the toner, which was -2hc/g.

Comparative Example 8 An experiment was conducted in the same manner as in Example 11 except that copper oxide particles were not added. The initial image had a reflection density of 0.9 to 1.1, and the image was slightly foggy and had toner scattered around the characters. Obtained. When copying was continued, the reflection density changed, and after about 50 to 150 copies, the reflection density was 0.7 to 0.8.
Then, after about 500 sheets, the initial reflection density was reached again. Furthermore, when this was left for 40 days and then copied, the resulting copied image had a reflection density of 0.6 to 0.
It was a poor quality with a rating of 8, with a lot of fogging and severe shading around the letters.

Comparative Example 9 Example 12 except that tantalum oxide particles were not added.
When I conducted a similar experiment, I found that the initial image had a reflection density of 0.9~
1.0, and an image with a slight foggy appearance and toner scattering around the characters was obtained.

When I continued copying, the reflection density changed to 150.
The reflection density became 0.6 to 0.7 after about 500 sheets, and reached the initial reflection density again after about 500 sheets. Further, when the copy was made after being left for 40 days, the obtained copy image had a reflection density of 0.6 to 0.8, and was of poor quality with a lot of fog and severe shading around the characters.

Comparative Example 10 An experiment was carried out in the same manner as in Example 13 except that strontium oxide particles were not added, and only the same results as in Comparative Example 9 were obtained.

Comparative Example 11 An experiment was carried out in the same manner as in Example 14 except that lanthanum oxide particles were not added, and only the same results as in Comparative Example 9 were obtained.

[Brief explanation of drawings]

FIG. 1 shows Example 1. FIG. 2 is a graph diagram showing the relationship between the number of durable sheets and image reflection density in the developers of Comparative Examples 1 and 2, and FIG. 2 is an explanatory diagram schematically showing an apparatus for measuring the tripo charge amount. 1...Suction machine, 2...Measurement container, 3...Conductive screen, 4...
...Lid, 5...Vacuum gauge. 6...... Wind force control valve, 7... Suction port. 8... River... Capacitor. 9・・・・・・・・・Electrometer.

Claims (1)

[Claims] (1) a negatively charged toner, a hydrophobized negatively charged silicic acid fine powder that has a higher triboelectric chargeability than the toner and has a particle size of 3 μm or less; is larger than the silicic acid fine powder and smaller than the toner, the volume average particle diameter is 1.0 to 4.0 μm, the loss on heating up to 100°C is 0.5% by weight or less, and the nitrogen gas adsorption B by law
A negatively charged developer comprising at least the following: a microdisperser having an ET specific surface area of 15 m^2/g or less.